Anitioxidative activities againt 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical were evaluated for ten diarylheptanoids, $1,7-bis-(3,4-dihydroxyphenyl)-heptane-3-O-{eta}-D-glucopyranosyl(1{ ightarrow}3)-{eta}-D-xylopyranoside(1)$, $1,7-bis-(3,4-dihydroxyphenyl)-heptane-3-O-{eta}-D-apiofuranosyl(1{ ightarrow}6)-{eta}-D-glucopyranoside(2)$, $1,7-bis-(3,4-dihydroxyphenyl)-heptane-5-O-{eta}-D-glucopyranoside(3)$, 1,7-bis-(3,4-dihydroxyphenyl)-5-hydroxyheptane(4), $1,7-bis-(3,4-dihydroxyphenyl)-heptane-3-one-5-O-{eta}-D-glucopyranoside(5)$, oregonin(6), hirsutanonol(7), hirsutenone(8), $1,7-bis-(3,4-dihydroxyphenyl)-5-hydroxyheptane-3-O-{eta}-D-xylopyranoside(9)$ and platyphylloside(10), which were isolated from Alnus japonica. Aglycones (4,7 and 8) and mono glycosides (3,6 and 9) showed more strong antioxidative activities than diglycosides (1 and 2) against the DPPH radical. Especially, hirsutenone(8) showed superior activity among ten diarylheptanoid.